1. Field of the Invention
This invention relates to humidifiers that are used in forced hot air heating systems. Specifically, this invention relates to an improved apparatus and method for introducing steam into a heated air stream in such a system.
2. Description of the Prior Art
It is well known that forced air heating systems tend to create an atmosphere in a building space characterized by low relative humidity which leads to occupant discomfort and possible health problems, damage to wooden articles including furniture contained within the building, and the discomfort caused by static electricity discharges. To obviate these problems, it is common practice to employ devices for adding moisture to the air being forced through the building space. In this regard, a wide variety of devices are commonly employed. For example, evaporative type systems are installed in the furnace plenum or heating ducts so that heated air is forced to flow through and about sponge-like members that are maintained in a moist condition by placing them in contact with a water reservoir. Such reservoirs must be maintained at a preset level to ensure sufficient moisture content in the sponge-like members. It is also known to utilize a steam generator in combination with a forced air heating system to place water vapor into the heated air stream. The steam is generated by use of a submerged heating element in a water reservoir tank. The water level must be maintained in such a tank at a predetermined level to keep the heating element submerged. Steam rises from the water level surface through a pipe or duct in communication with the forced air system and is thereby introduced into the heated air stream.
The systems of the prior art have several disadvantages. Systems that rely on evaporation also remove heat from the heated air in the system through the evaporation process, thus requiring additional energy to heat the serviced environment to the level demanded by the occupant or use. Furthermore, it has been found that steam mixes into the air stream better, providing a uniform water content in the heated air. These systems also rely on water reservoir tanks which have the disadvantages described below.
All of the known steam humidifiers rely on the use of a water reservoir tank or a city/utility provided source of steam. The water reservoir systems provide a tank of standing water that can be a breeding ground for bacteria, molds, and other unhealthy agents. Furthermore, water reservoir based systems cannot be run continuously because such systems must be periodically shut down to replenish water supply within the reservoir when it drops below a preset level.
While systems relying on steam generated by a city or utility overcome the aforementioned problems, such steam hookups are not widely available and are practically never provided for suburban residential use.
Accordingly, one important object of the present invention is to provide an improved steam humidifier unit for use with a forced air heating system.
In carrying out the foregoing and other objects, the present invention contemplates an improved method of generating steam to be injected into the forced air system. In its broadest respects, the invention contemplates a steam generator that connects to a continuous pressurized source of water such as a municipal water hookup, converts water supplied by the continuous pressurized source into steam and sprays that steam through a nozzle into the heated air system.
In one embodiment theater line connected to the continuous pressurized water source is controlled by a valve that opens in response to control circuitry, and a heating clement operates to convert water to steam only when water is flowing in the water line.
In another embodiment the water line connected to the continuous pressurized water source is controlled by a valve that opens in response to control circuitry, and a heating element operates to convert water to steam also in response to control circuitry wherein the heating element will be deactivated and the water valve will be closed if the heating element becomes too hot, the heater shuts down, or no more humidity is required.
In still another embodiment a heating and humidifying system having a return duct, a furnace, and a plenum is provided wherein a humidity sensor compares humidity in the return duct to a preset value and a thermostat compares the ambient temperature in the serviced room or building to a preset value. If both heat and humidity are demanded based on the preset values, a control valve causes water to flow from the continuous pressurized water source in heat transfer relationship with a heating element and the heating element is activated in response to the water flow and converts the water into steam which is then sprayed into the plenum of the furnace.
A method for controlling humidity is also disclosed including the steps of providing a heating system having a return duct, a furnace, and a plenum, sensing the humidity in the return duct, sensing the state of the furnace, causing water to flow through a water line when both humidity and heat arc required, heating the water thereby converting it to steam, and spraying the steam into the plenum of the furnace.